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Replacing external oil burner with a Monobloc ASHP

  • 30-06-2022 2:29pm
    Registered Users Posts: 454 ✭✭


    My house is circa six years old. We installed an external oil burner at the time, but we doubled down on the insulation and air tightness.

    Now we're considering replacing the oil burner with a monobloc ASHP. Presuming that all our radiators and temperature sensors are compatible, would it be just a matter of lifting out the external oil burner and installing the monobloc ASHP ? ie no work would need to be done on the internal house ? it seems it should be more complicated than that ?


  • Registered Users Posts: 10,017 ✭✭✭✭the_amazing_raisin

    Unfortunately there's no clear cut answer

    Typically a heat pump doesn't reach the same temp as an oil boiler. Low temp heat pumps typically output water around 35C, there are higher temp models which are designed as drop in replacements for a gas or oil boiler, output from these is generally around 65C

    The low temp ones are more efficient, whether you can go with one depends on your current heating system. Lower temp water means you'll need bigger radiators and pipes to achieve the same heat output

    If the heating system was designed with an eventual changeover to a heat pump in mind, then chances are you can just do a drop in replacement. If any of the rads are too small then you might need to replace them with bigger rads or look into a high temp heat pump

    The other thing you'll need to look at is the electrical connection. A heat pump is a bit more power hungry than an oil boiler so you may need a bigger fuse or possibly rewiring

  • Moderators, Home & Garden Moderators Posts: 4,486 Mod ✭✭✭✭graememk

    A condensing boiler (either oil or gas) is most efficient at lower temperatures anyway and the house is only 6 yrs old, it's likely it has been designed with lower temperatures in mind. (Check out urban plumber on YouTube, he's a good video on how a lot of condensing gas boilers are running inefficiently because they are actually too big!)

    So swapping it out with a heatpump should be straight forward.

    But without anymore information with the specifics of your system it's gonna be hard to tell.

  • Registered Users Posts: 5,899 ✭✭✭Ubbquittious

    Is there actually a monobloc heat pump that will go to 65 easily?

  • Registered Users Posts: 97 ✭✭fael

    You can also get rads that are made for low temps, to work better with heat pumps.

  • Registered Users Posts: 2,875 ✭✭✭Borzoi

    in a nutshell: no

    Most current models use R32 as the refrigerant, and this means effectively they're limited to 60C. 55C would be what most can realistically achieve

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  • Registered Users Posts: 152 ✭✭curioustony

    Pity. I read some articles about propane and CO2 as refrigerants. Opened the door to a direct swap of the oil burner. Seemed very promising and a lot easier than a deep retrofit.

    Need to wait for the industry to catch up with the technology I suppose.

    🌞4.55 kWp, azimuth 136°, slope 24°, 5kW, 🛢️10.9kWh, Roscommon

  • Registered Users Posts: 9,602 ✭✭✭antoinolachtnai

    It really depends! If the house is warm enough that you don’t run the oil much then it might work. You might be able to make up for the lower water temperature by running the heat pump for longer than you currently run the oil burner for. You could also add a few extra radiators and that might make a difference too. You could even leave the relatively new oil boiler in place as a backup for the coldest days. But it all depends.

  • Registered Users Posts: 72 ✭✭Punchin A Keyboard

    I am thinking the same as i starting the one stop shop nonsense but no ufh only rads. There are some R290 propane heat pumps from nibe and vissemann allegedly up to 70c i have seen a blog about one installed in Kildare

  • Registered Users Posts: 5,899 ✭✭✭Ubbquittious

  • Registered Users Posts: 72 ✭✭Punchin A Keyboard

    I think they have to be mono blocks due to the kaboom nature of propane. No splits there. No idea what goes in through the wall, i assume it's water and that they have frost protection or some drain in the case of cutoff in cold weather

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  • Registered Users Posts: 195 ✭✭UID0

    The only way to be sure is to get someone to calculate the radiator power requirement for each room and the amount of power that will come out of your radiators at a lower flow temperature. You may require some radiators changed or not, depending on the results of the calculation. You also may need a new hot water cylinder or a buffer if there isn't enough water in your heating system.

    If there aren't any of those upgrades required, then the only internal work will be electrical cabling. The heat pump will require significantly more electrical power than the oil burner, so the power cable and control cables will have to be run from your consumer unit and wherever your controller is going out to the heat pump. The immersion controller may have to replaced/installed as well so that the heat pump can turn it on to run its ant-legionella cycle (usually once a week).